1. Field of the Invention
The present invention relates to the field of expert systems, and more particularly to an expert system and method for diagnosing faults in equipment.
2. Description of Related Art
Knowledge systems such as expert systems are computer systems that emulate reasoning tasks used by human experts. Such knowledge systems typically use an "inference engine" to interpret encoded knowledge of human experts which is stored in a "knowledge base." If the domain of the knowledge base or scope of the problem is sufficiently narrow, and a sufficiently large body of the knowledge is properly coded in the knowledge base, then the expert system can achieve performance matching or exceeding the ability of a human expert.
Previous attempts to build such expert systems have been based upon a symptom diagnostic rules approach. The essence of this approach is as follows. For every symptom, initial or intermediary, there should correspond an ultimate or intermediary cause. An explicit procedure that leads to a correlation of a symptom to its cause is called a symptom diagnostic rule. These diagnostic rules may be manipulated by a "rule firing" inference engine as follows. Suppose symptom X is exhibited by a given piece of equipment. The inference engine searches for a diagnostic rule in the collection of such rules which forms the knowledge base. If there is a rule that corresponds to the symptom, then we take the prescribed action Y. If the equipment is restored to normal operation by taking the action Y, the troubleshooting process is completed. If the ultimate cause is not found after the action Y was taken, then a new symptom X.sup.1 is generated. The inference engine then looks for another rule that corresponds to symptom X.sup.1.
While such expert systems have generally been found useful in the diagnosis of electronic equipment, such systems often had at least one significant disadvantage involving the process for constructing the diagnostic rules. It is almost impossible to anticipate all or even most of the possible symptoms of complex electronic systems and to identify all possible causes for the symptoms. It is also very difficult to develop the correlation procedures between the diagnostic rules. Accordingly, the chief disadvantage of using prior art expert systems to perform diagnosis on electronic equipment is the necessity of constructing the system diagnostic rules.